1. Field of the Invention
This invention relates to the manufacture of chip-on-glass devices. More particularly, this invention relates to improved systems and methods for preventing damage due to electrostatic discharge during the manufacturing process.
2. Description of Certain Related Technologies
Microelectromechanical systems (MEMS) include micro mechanical elements, actuators, and electronics. Micromechanical elements may be created using deposition, etching, and or other micromachining processes that etch away parts of substrates and/or deposited material layers or that add layers to form electrical and electromechanical devices. One type of MEMS device is called an interferometric modulator. As used herein, the term interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In certain embodiments, an interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. In a particular embodiment, one plate may comprise a stationary layer deposited on a substrate and the other plate may comprise a metallic membrane separated from the stationary layer by an air gap. As described herein in more detail, the position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Such devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of these types of devices so that their features can be exploited in improving existing products and creating new products that have not yet been developed.
MEMS devices, as well as other forms of micro-circuitry including, e.g., LCD devices and OLED devices, may be damaged during manufacture due to electrostatic discharge (ESD). ESD may occur when two proximate electrodes have different respective electrostatic charge levels. In order to prevent ESD, all leads that are in proximity of each other and are connected to micro-circuitry susceptible to damage by ESD should be electrically connected to a common shorting circuit.
Prevention of ESD in manufacturing commonly includes the use of a shorting bar in TAB (Tape Automated Bonding) configuration. All the elements are connected to the shorting bar with electronic leads that will later drive the elements being protected from ESD. After the manufacturing process has concluded, the leads are cut using a saw or a scribe and break technique. The leads are then bonded to a TAB circuit built on a flexible material, such as polyimide. The TAB connects the display to driver chips between the glass of the display and the input circuitry behind the display.
As device geometry is being continuously reduced for lower cost and lighter weight, the COG (chip-on-glass) approach has become a favored configuration. The configuration of I/O bond pads used for the COG approach does not lend itself to the use of a single shorting bar in TAB configuration. Any mechanical cutting in the bonding area is prohibited. There is also very little space in the boding area for routing all the leads. This is especially true for display devices with large numbers of rows and columns.
Previous methods of preventing ESD in conjunction with a COG configuration have compromised on the ESD protection by utilizing partial shorts. Other methods have utilized cross-over structures in routing links to shorting bars which complicates the fabrication process and adds cost. What is needed is a method of providing ESD protection during a manufacturing process for fabricating devices including a COG configuration.